Update io.py

[elkolbo]

Comments and error messages in function now resemble functionality

PR Summary

The error message and the description of this function did not fit its functionality.
The expected string has to be a combination of point attributes. Intensity etc wont be accepted.
Changig this is not possible without changing usage. Therfore referral to other function.

Testing

In order to ensure this PR works as intended, it is:

• unit tested.
• [x ] other or not applicable (additional detail/rationale required)
  no testing needed. Only changes comments and error messages.

Compliance with Standards

As the author, I certify that this PR conforms to the following standards:

• [ x] Code changes conform to PEP8 and docstrings conform to the Google Python style guide.
• [x ] A well-written summary explains what was done and why it was done.
• [ x] The PR is adequately tested and the testing details and links to external results are included.